Eggs kept at room temperature: In the US, eggs undergo a sterilization process against salmonella where they are washed and sprayed with a disinfectant.
Leaving babies outside (in Denmark): Parents often leave their babies outside in their strollers while they go into restaurants and shops in Denmark.
How old everything is: If a building is from the 1800s in the US, it’s quite significant, but there is so much architecture in Europe dating far beyond the time when the US was even an idea.
Nudity: Many women in Europe aren’t afraid to take their tops off at the beach or pool, meanwhile public nudity is outlawed in many parts of America.
Laundry machines in the kitchen: Of course this varies across European countries, the reason being it was easier in days of less sophisticated plumbing to keep the things.
Lack of air conditioning: Both in homes and establishments, Americans are often surprised at the lack of air conditioning and heating systems in Europe.
Lack of window screens: Americans are always surprised to see a window without a screen, just letting in all the bugs.
No ice in the water: You can get natural water or refrigerated water in Europe, but you won’t often see the ice cubes that Americans are used to.
So many kinds of toilets: In the US, the toilets are all pretty much the same in that you sit on it and reach behind you to flush.
Paying to use the bathroom: In public spaces like train stations and shopping malls in some European countries, there can be a small fee to use the bathroom.